Pharmacokinetics and Safety of Rifamycin SV after Single and Multiple Doses of MMX(®) Modified Release Tablets in Healthy Male and Female Volunteers

The primary objective of this single- and multiple-dose pharmacokinetic study was the investigation of rifamycin SV’s pharmacokinetic profile in plasma and urine. All the 18 enrolled healthy men and post-menopausal women received modified release tablets containing 600 mg of the oral non-absorbable antibiotic, rifamycin SV, according to a multiple dose regimen: one tablet three times a day (daily intake: 1800 mg) for 14 consecutive days. Blood sampling and urine collection were performed up to 24 h post-dose after the first dose on Days 1 and 7. On average, on Day 1, C(max,0–24) was 5.79 ± 4.24 ng/mL and was attained in a median time of 9 h. On Day 7, all the subjects had quantifiable levels of rifamycin SV in plasma at each sampling time. After a peak concentration attained 2 h post-dose (mean ± SD concentration: 10.94 ± 16.41 ng/mL), rifamycin SV decreased in plasma to levels similar to those of Day 1. The amounts of rifamycin SV excreted in urine paralleled the plasma concentration at the corresponding times. On Day 1, the total amount excreted in urine was 0.0013%, and was 0.0029% on Day 7. The study results confirmed those of the previous Phase I study: the systemic absorption of rifamycin SV was also proved negligible after 7 days of the 600 mg t.i.d. dose regimen of the newly formulated tablets, currently under development for the treatment of several small and large intestinal pathologies, including diarrhea-predominant irritable bowel syndrome, hepatic encephalopathy, and others. Registered at ClinicalTrials.gov with the identifier NCT02969252, last updated on 26JAN18.